In a high pressure gradient pump, each different mobile phase is delivered by an individual pump head and then the mobile phases are mixed at the pump outlet. In a low pressure gradient pump, different mobile phases are mixed using a valve before entering the pump head.
As a result of the fact that the low-pressure gradient design uses only one pump head, it is of lower cost. It can also use more types of mobile phase without significant increase of cost.
Since solvent mixing point is much closer to the column head in the high-pressure gradient design, it provides a much faster gradient. This is measured using delay volume. The value can be 50-300 uL for high pressure gradient pump and can be 2 to 3 times larger for a low pressure gradient pump. A small delay volume is important when the analysis time is short or the flow rate is low. If the delay volume is too large, it become impossible to obtain reproducible gradient run since the planed composition cannot reach the column head before a run is finished.
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In high-pressure gradient HPLC, the mobile phase is pressurized to deliver a gradient of solvent mixtures. This allows for more precise control over the separation of compounds based on their differing affinities for the stationary phase. In contrast, low-pressure gradient HPLC operates at lower pressures and uses a manually adjusted gradient system, providing less precise control over the separation process.
HPLC UV detector is a component used in high-performance liquid chromatography (HPLC) to monitor eluent absorbance, while a spectrophotometer UV detector is a standalone instrument used to measure the absorption of light at different wavelengths. HPLC UV detectors are specifically tailored for chromatography applications, whereas spectrophotometer UV detectors are more versatile and used for various analytical purposes.
GLC (Gas Liquid Chromatography) uses gas as the mobile phase and liquid as the stationary phase, while HPLC (High Performance Liquid Chromatography) uses liquid as the mobile phase and a solid or semi-solid stationary phase. GLC is mainly used for volatile compounds, while HPLC is more versatile and can analyze a broader range of compounds.
Reverse phase and normal phase HPLC techniques differ primarily in the polarity of the stationary phase and mobile phase. In reverse phase HPLC, the stationary phase is nonpolar and the mobile phase is polar, while in normal phase HPLC, the stationary phase is polar and the mobile phase is nonpolar. This polarity difference affects the retention and separation of compounds in the sample.
In reverse phase HPLC, the stationary phase is nonpolar and the mobile phase is polar, while in normal phase HPLC, the stationary phase is polar and the mobile phase is nonpolar. This difference in polarity affects how compounds interact with the stationary phase, leading to variations in separation and elution times.
The resolution factor in HPLC is used to quantify the degree of separation between two adjacent peaks on a chromatogram. It is calculated by dividing the difference in retention times of the two peaks by the sum of their peak widths. A higher resolution factor indicates better separation between the peaks.